Dehydrator



Feb. 27, 1945.

J. O. REED DEHYDRATORS Filed Sept. 22, 1942 5 Sheets-Sheet 1 5 mmmiINVENTOR I J.0.REED ,g/Q 9 m,

QM. law Y ATTORNEYS Feb. 27,1945. J. o. REED 2,370,422-

DEHYDRATORS Filed Sept. 22,19 42 5 Sheets-Sheet 2 INVENTOR J'.O.REED

AT ORNEYS l I I I I I I I I I I I I I I l I I I I I J. o. REED Feb. 27,1945.

DEHYDRATORS 5 Sheets-Sheet 3 Filed Sept. 22, 1942 INVENTOR J .O-REED ATORNEYS Feb. 27, 1945. ED 2,370,422

DEHYDRA'IORS Filed Sept. 22, 1942 5 Sheets Sheet-4 I HUM-g INVENTORJ.O.REED

Feb. 27, 1945.

J. o. fiEED 2,370,422

DEHYDRATORS Filed Sept. 22, 1942 5 Sheets-Sheet 5 ATTORNEYS PatentedFeb. 27, .1945

UNITED STATES PATENT OFFICE Jesse 0. 41. 12532? minor to Claude it.Wiokard, as Secretary of Agriculture of the United States. of America,and hi moeslcrs inoilice (Granted under the act of March 3,

ms. at

April 30, 1 9 28; 370 0. G. 75'!) This application is made under the actof March 3, 1883, as amended by the act of April 30, 1928, and theinvention herein described, if patented, may be manufactured and used byor for the Government of the United States of America for governmentalpurposes without the payment to me of any royalty thereon.

This invention relates to dehydrating apparatus, particularly useful inthe dehydration of food products.

At present, two general types of dehydrators, known as the cabinet andtunnel types, are in use. In the cabinet type, the food products areloaded on open trays which are placed in a closed cabinet, and dryingair or other gas is circulated over them to remove the desired amount ofvaporizable water. The trays are then removed, and the process isrepeated for each batch. 'In the tunnel type the process is continuousrather than in batches. The trays of food products are started at oneend of the long timnel, and means is 'provided to move them graduallytoward the other end. Drying air or gas is circulated in the tunnelthroughout its length so that during the waste both in the heat and inthe power required to circulate the air through zones in which nodehydrating is being accomplished.

'of dehydrating: the provision pf an apparatus type dehydrator.

passage of the trays the food products are de- 1 hydrated.

The tunnel type has certain'advantages .over

the cabinet type. In large scale operations, a continuous process ismore desirable than a batch process. The flow of materials in acontinuous process is more even and regular-and fewer operations arenecessary. v

The usual tunnel type also has several disadvantages, however. The airpasses lengthwiseof the tunnel from one end to the other, and it cannotbe kept at the same temperature or relative humidity throughout.Ordinarily, the tunnel can not operate successfully at the same timeupon diflerent types ofproducts requiring diflerent con ditions oftemperature and humidity. Also, in dehydrating certain food products, itis desirable to subject them at some point in the process to treatmentsother than dehydrating, such as blanching. This can be accomplished withsome types of cabinet dehydrators, but not with usual tunneldehydrators, since all the food products in the tunnel are operated uponsimultaneously with respect to one operation or another. There is alsoloss in the starting and stopping of'the tunnel type of dehydrators. Theentire tunnel must be conditioned when the first trays are startedthrough at the beginning of the run, and maintained until the last traysof the run have passed completely through. This involves a Among theobjects of this invention are the provision of a dehydrating apparatuswhich combines the advantages of both the tunnel type and the cabinettype; the provision of a flexible dehydrating apparatus adapted tolusefor dehydrating all types of food products; the provision for obtainingand maintaining all desired conditions which is convertible from a unittype to the tunnel type by the mere addition of similar units; theprovision of an apparatus of few parts which can be made into a unittype or a tunnel type at will; and the provision of improvements incabinet type dehydrators generally.

Other objects of the invention will be apparent I from the followingdetailed description and attached, drawings, in which,

Figure l is a perspective view showing several cabinet units joinedtogether, forming a tunnel Figure 2 is a section ontne line 2-2 of Fiure 1 h I Figure 3 is a section on the line 3-4 of Figure "2, certainparts being brokenaway to illustrate the'st'ructure more clearly.

' Figure 4 is a side view of an improvedcabinet type of dehydrator. I

Figure 5 is an enlarged section on the line 5-5 of Figure 4.

Figure 6 is an enlarged section onthe line 6-5 of Figure 4..

Figure '1 is a perspective view of a tray suitable for use in any of thedehydrators.

' Figure 8 is an exploded three-dimensional view of a modified tray andbailie suitable for use in any of the dehydrators.

Figure 91s a sectional view of a few trays and banles of the type shownin Figure 8, showing the manner of operation.

Figure. 10 is athree-dimensional view of one of the bailles of Figure 8.

Referring to the drawings, and in particula to the apparatus of Figures1, 2 and '3, similar. separable individual cabinet, units l, 2 and 3 areshown. coupled together in Figure 1. Three units I are shown, althoughthe apparatus is adapted to any number, and may have as many as six ormore for carrying out the most complete process.

The various constructional details which are obcabinet dehydrator initself. It provides a drying or processing chamber 4 into which a truck5 loaded with trays 6 may be pushed. Guide rails I, provided on thefloor in the drying chamber, properly position the truck. Each trayshown in detail in Figure '7 is provided with end pieces 8 and open sidepieces 9. Figure 3 shows a double row of trays stacked one on the other,with the end pieces forming partitions which close the ends of th dryingchamber. Air to pass over the trays is admitted and exhausted throughthe open side pieces 9, which restrict the area and, act as a grille tocontrol the delivery of air over the trays. The total inlet and totalexhaust areas provided by the open side pieces should be substantiallyequal to the cross-sectional area of the fan exhaust duct to maintain asubstantially constant air velocity.

The floors of the trays are shown as formed from spaced apart slats l0,although screen may be used. The tops H have solid floors I2 forming aceiling for the drying chamber. It may be observed, when severalindividual cabinet units are arranged as shown in Figure 1 and no trucksare present, that a tunnel results.

The trucks and trays are of a predetermined definite length relative tothe individual cabinet units, so that they may be pushed into the tunnelat one end, and when the rear truck is stopped at its proper location,all other trucks will be properly positioned. In order to isolatetheindividual chambers of the several cabinet units from each other,flexible flaps I3, acting as seals, are fixed in the chambers atpositions near the junctures of the individual cabinet units to engagethe ends of the trays when the trucks are properly positioned. Theseflaps allow the trucks and trays to pass, but they substantially preventgas circulation between the individual chambers in conjunction, ofcourse, with the end pieces of the trays and the solid floors of thetops.

The various cabinet units are secured together with flanges and bolts,as shown at ll. Each unit has openings in its opposite end walls for theadmission and egress of products-to be dehydrated, and the several unitsare connected together with the openings matched. The end units areprovided on their free ends with suitable doors i5, which can be removedand flanges substituted,if other units are to be added on the ends. Ifonly one cabinet unit is desired, doors are generally provided at bothits ends, although the'doors may be omitted.

Each cabinet unit is provided with a circulating and heating means. Afan [6, preferably of the forced feed multiple type, is located incompartment I'I above the unit. The fan is driven by a variable speedmotor (not shown) and circulates air through a heater l8, which maybe ofany desired type, but is preferably a steamheated radiator, a connectionof which is shown at ii. The heated air leaves each fan unit through anexhaust duct 20 and is forced through chamber 2| which is provided withdeflecting fins 22 to distribute the air evenly over the sides of thetrays.

After the air passes over the trays and has gathered moisture from thefood products, it enters exhaust duct 23 from which it is directedpartiall or wholly to the outside atmosphere by a suitable dampersystem. An air inlet port is provided at 24, the opening of which iscontrolled by a valve 25, which may be held set in a selected positionby adjusting means 26. An air outlet port is provided at 21, the openingof which is controlled by damper 28, which may be held set in a selectedposition by adjusting means 20. Damper 28 also acts as a deflector todirect the air into the outlet port. As can be seen in Figure 3, thedamper in one extreme setting will direct all th outlet air to theoutside, and in the opposite extreme setting will direct it all 'backinto the heater.

The function of the damper system is to control the humidity of thedrying air. Any part of the exhaust air may be returned to the heaterrather than to the outside atmosphere. Returning larger quantities ofthe exhaust air to the heater increases the humidity of the drying air.

Suitable instruments, such as a dry bulb thermometer 30 and a wet bulbthermometer 30', may be positioned in the drying air current forobservation, whereby manual adjustments can be made on the heat admittedto the heater for maintaining the desired dry bulb temperature and onthe damper system to maintain the desired wet bulb temperature of thecirculating air.

Each cabinet unit is provided with means rendering it useful for othersteps than drying. A perforated steam pipe is provided at 3i, to admitsteam for blanching purposes. This pipe may also be used for increasingthe relative humidity of the air, as may be necessary at the start ofdehydrating a new batch, for example. By completely closin ports 24 and21 and admitting steam, blanching can be carried out to any desiredextent. The chamber can then be immediately aerated and drying startedby simply shutting oil? the steam and resetting the damper system.

If it is desired to treat the food products with flue gas or sulphurdioxide, as is necessary in some cases to inhibit nzyme reactions, suchgases are admitted through the inlet port 24.

The adaptability of this-apparatus to a wide variety of conditions anduses is apparent. A complete process may be carried out with one cabinetunit, by successively effecting different processing steps on a batch ofproducts loaded in the unit. If, however, it is desirable to operateseveral units together as a tunnel, each may be set and made to performany desired step such as blanching, gas treatment or drying. Toillustrate, the first cabinet unit may be used for blanching or used forgas treatment to inhibit enzyme reactions, or if separate units aredesired for these treatments, the first and second may be thus employed.In the next unit dry gases may be used and circulated with highvelocity, since the food product is heavy at this stage. In the next twounits, the drying may be eifected at increasing temperatures and atdecreasingly lower air velocities, to prevent blowing the light, dry

products oil! the trays. All units may be operated at the same time ondiiferent batches, the trucks being pushed ahead to convey the productsfrom one unit to the next unit.

Referring to the modified type of Figures 4, 5 and 6, the cabinet typeof dehydrator herein shown is generally similar to the cabinet unit usedin Figure 1. It provides a processing chamber 40 into which the truck 4|i pushed. The truck in this instance is provided with guide wheels 42 atits centerrunning between rails 43. The trays 6 are the same as thosedescribed above.

It may be desirable to run various size batches, and means in this formprovides for blocking oi! air from the part of the chamber not occupiedif the truck is loaded to less than its full capacity.

as a weight at its free hanging end. The other end of the curtain,provided with a stifl'ener 41,

is attached to a pull rope 48, which extends outside the dehydrator, andis wound on a bracket 49. When the truck is in position, the operatorcan readilyadjust the curtain to block oil all the air inlet area abovethe top tray.

The fan- 50 and heater of this dehydrator may be acommerciallyobtainable heating unit of predetermined capacity, if desired, and ifconstant heat and air are supplied, the tray capacity can be adjusted tocare for varying conditions.

A blanching steam admission pipe 52, similar to that described inreference to the first modification, is provided.

Air is exhausted from the fan through exhaust duct 53, and passes a setof fin 5454--5l, ad-

justably mounted on axes 54-54'--54' to direct the air over the sides ofthe trays.

In the damper system of this modification, the air inlet port 55 iscontrolled by a valve 56, and the air outlet port 51 is controlled bydamper 58. The valve and damper are so coupled together that when thevalve is opened to admit dry outside air, the damper is set to open theair outlet port and to deflect the air away from the heater and out ofthe port. Figure 5 shows an extreme setting of the system inwhich all ofthe air is deflected to the outside. The coupling is provided by a link89 connecting crank arms 56' and 58' attached to the valve and damper,respectively, at their pivotal axes. A control rod 60 for setting thedamper system is attached to the damper crank arm 58.

Observation dry and wet bulb thermometers are shown at 6! and 84,respectively, which may be used in connection with manual control meansas described in reference to Figure 3. Automatic control is, however,preferable, and may be provided by the following described means shownschematically.

A modulating motor control 6| of known type canbe coupled to the controlrod, and the damper system regulated automatically to maintain a desiredhumidity by coupling the motor control to a humidostat or wet bulbcontrol apparatu of wellknown type, located in the box shown at 81.

' The dry bulb temperature may be controlled by a thermostat or dry bulbcontrol apparatus also automatic control of the dry bulb temperature,

a very efiicient heat consumption is obtained, as no excess air isheated or exhausted.

Inspection windows are provided at 65, 68 and 61.

In the embodiments thus far described, the trays provide for circulatingthe air over the food products. Figures 8, 9 and are directed to animproved tray system in which the air is forced to circulate through thetray floors or screens. with some products, this results in a moreunliorm drying, and makes it possible to'load the trays deeper. The tray10 is provided with side and end walls H and 12, resp ctively, of thesame height, and a perforated floor I3, herein shown as a screen. Abaflle 14, positioned between each pair of screens, is provided withsolid end walls II of the same height and a solid floor 18. Eachproducts loaded on the trays.

side wall of the baille, however, is open above the floor on one sideand below the floor on the other side, as shown at 11, but is otherwiseclosed by pieces II.

The trays and baiiles are alternately stacked, as shown in Figure 9. Dueto this arrangement, the air is forced to travel as shown by the arrows,and is forced through the tray floors and food Strips may be fastened tothe end walls 15 of baffles 14 so as to hold said bailles in spacedapart position, and the trays Ill may be slid between the ballles.

Having thus described the invention, what is claimed is:

1. A dehydrating apparatus comprising at least two separate, similar,individual cabinet units, each unit having an opening in each of its endwalls for the admission andegress of products to be dehydrated and eachunit being provided with means for effecting a first gas-processing stepand with means for effecting at least one more gas-processing stepdifferent from that of gether with the openings matched to form a tunneltype dehydrator, whereby when so connected together the first unit maybe employed to eflect the first processing step on a first batch ofprod-' ucts loaded in the first unit, following which the first batch ofproducts may be conveyed into the second unit and a second batch ofproducts placed in the first unit and the second unit may be em-' ployedto effect the second processing step on the first batch of productswhile the first unit is circulation between the individual units whenthe said units are connected together.

2. A dehydrating apparatus comprising at least two separate, similar,individual cabinet units,

each unit having an opening in each of its end walls for the admissionand egress of products to be dehydrated, trays having closed ends soconstructed that when the trays are stacked on each other the ends forma closed wall, each unit being provided with means for eflecting a firstgasprocessing step and with means for efiecting at least one moregas-processing stepdifferent from that of the first-mentioned means,whereby a single unit may be employed to effect the first processingstep followed by effecting the next processingstep on a batch ofproducts loaded on the trays imthe unit, and means for detachablyconnecting the'units together with the openings matched to form a;tunnel type dehydrator, whereby when so connected together the firstunit may be employed to effect the first processing step on a batch ofproducts loaded in the first unit, following which the first batch ofproducts may be conveyed into the second unit and a second batch orproducts placed in the first unit and the second unit may be employed toeffect the second processing step on the first batch of products whilethe first unit is effecting the first processing step on the secondbatch of products, and inwardly extending flexible flaps fixed in thetunnel near the ,junctures of the individual units, the flaps engagingthe stacked trays and forming with the closed wall means for preventinggas circulation between the individual units and permitting the trays tobe conveyed from the first unit into the second unit.

3. In a dehydrator, a tray system comprising removable trays each havinga perforated floor and solid side and end walls, said side and end wallsbeing of the same height, and removable baflles corresponding in size tothe trays, said bailles each comprising a solid floor, solid end wallsextending above and below the floor, one.

